The prior art has suggested adding combustion improvers for diverse types of fuel usages including flame burners, diesel engines, gasoline internal combustion engines and various turbine configurations. Each type of combustion apparatus has its unique characteristics in terms of supply, oxygenation, combustion and exhaust, and additives have largely been designed to meet specific needs. The prior art has employed a variety of additives, some in liquid form, some with liquid carriers, and some solid, as the particular needs of the combustion system and its interaction with the additive has required. The following citations are representative of the diversity of additives, physical forms and conditions of use.
U.S. Pat. No. 2,843,200 to Rocchini, is concerned with reducing the corrosiveness of vanadium compounds in fuels. Rocchini discloses adding finely-divided precipitated hydrated calcium silicates where vanadium corrosion is a problem. The level of addition is based on the vanadium content of the fuel. The calcium silicates are said to change the nature of the resulting vanadium-containing ash but are not disclosed as improving combustion per se.
U.S. Pat. No. 2,402,427 to Miller et al discloses treatment of fuels for diesel engines to increase their cetane numbers--thus improving engine performance. This is done by contacting the diesel fuel with a solid ignition promoter just prior to use, to dissolve relatively small amounts of the solid in the fuel. The ignition promoter is preferably heated prior to contact with the fuel to assure achievement of the desired concentration in solution, and any undissolved solid particles of ignition promoter are screened from the fuel prior to injection into the engine.
In U.S. Pat. No. 4,129,421, Webb discloses a catalytic fuel additive for use in engines or furnaces. The additive employs a solution of picric acid and ferrous sulfate in specified alcohols. An example shows the additive employed for use in gasoline engines at levels supplying less than 10 parts per billion of the combined catalysts. The disclosure indicates higher but unspecified levels of use for heavy fuel oils. In all cases the catalysts are fully dissolved in the fuel.
In commonly assigned EPO patent application No. 119,086A, filed by Osgerby, there is described a system for the continuous introduction of an admixture of a fluid and a catalytic material, such as a salt of a platinum group metal, directly into a combustion chamber. The catalytic material is selected so that the catalyst (e.g., metallic platinum) will rapidly be made available by the heat of combustion to enhance that combustion. Catalyst-containing materials such as chloro platinic acid (H.sub.2 PtCl.sub.6.H.sub.2 O), platinum tetrachloride (PtCl.sub.4), ruthenium chloride (RuCl.sub.3.H.sub.2 O), ruthenium oxide (RuO.sub.2.H.sub.2 O), palladium nitrate (Pd(NO.sub.3).sub.2), palladium sulfate (PdSO.sub.4.2H.sub.2 O), rhodium nitrate (Rh(NO.sub.3).sub.3.2H.sub.2 O), magnesium oxide (MgO) and manganese oxide (MnO) are disclosed as exemplary. When steam or water is employed as the fluid for admixture with the catalyst materials, exposure to the flame causes microexplosions of the water as it rapidly expands upon heating. These microexplosions shatter the oil droplets, yet further improving the combustion.
In U.S. Ser. No. 516,094, filed July 22, 1983 by Haney and Sullivan, also commonly assigned, a stable emulsion is prepared containing fuel and a dispersed phase which includes a catalyst material, preferably as part of a liquid medium. The catalysts exemplified here are of the type disclosed in the EPO application mentioned above. Rapid transformation of the dispersed liquid to the gas phase was disclosed to cause microexplosions which enhance combustion.
And, in commonly assigned U.S. Ser. No. 677,954, filed Dec. 4, 1984 by Bowers and Sprague, there is described a method for improving combustion which employs catalyst compounds which are soluble directly in the fuel and eliminates the need for aqueous or other carriers as well as for high-shear dispersing and emulsifying equipment and processing.
In U.S. Pat. No. 3,765,848, Brent discloses the addition of sodium tripolyphosphate in powdered form to a liquid hydrocarbon motor fuel to improve combustion. Brent suggests that there may be some interaction of the additive with the water which is always present to some extent in gasoline. At a concentration of about 10 PPM, the compound is said to promote cleaner and more complete combustion with no accumulation in carburators.
In U.S. Pat. No. 3,332,755, Kukin discloses combustion-improving additives for residual petroleum fuel, coal, coke, and fuel containing vanadium, sulfur or sodium. The disclosure noted that the prior art had injected into the firing zone comparatively massive dosages of materials such as the oxides, hydroxides, carbonates and other salts of magnesium, calcium, aluminum, zinc, sodium, silicon, manganese and various of the rare earth metals, as well as clays such as dolomite, talc, and magnesias. Noting that these additives had proved unsatisfactory because the large doses required would produce appreciable quantities of dense, tenacious ash, and cause other difficulties, there is disclosed an additive which contains low levels of iron and any two of aluminum, magnesium and manganese. The examples show additives containing iron as iron oxide, magnesium as the hydroxide (Mg(OH).sub.2), manganese as manganese dioxide (MnO.sub.2) and aluminum as aluminum hydroxide (Al(OH).sub.3), with these active materials dispersed in liquid containing an oil phase, surfactant, water, hydrophilic colloid, a glycol and pigment stabilizer. Where the additive is to employ relatively high percentages of aluminum, it is preferred that such be added as calcined alumina or a mixture of hydroxide (commonly referred to as hydrate) and calcined alumina. The active materials are preferably present in the liquid at particle sizes of from 0.1 to 10 microns and the disclosure exemplifies one additive, including the vehicle (about 50%) and combination of three essential metals, added to residual petroleum fuel in proportions of 0.035% by weight of the fuel.